The present invention relates to a mobile agricultural machine such as a combine for continuously reaping and simultaneously threshing grain stalks to be harvested.
It has been and is a common practice for drivers of the combines to drive each combine having a pair of right and left crawlers such that it runs along and harvests a row of grain stalks in a farm and then turns itself at an end bare area of the farm before advancing to the next row of grain stalks. The combine has therein a transmission receiving a traction power from an engine and outputting it to the right and left crawlers through a right-side and left-side clutches, respectively. When turning the combine at the bare end, the driver has to switch off one of those clutches to temporarily make idle one of the crawlers. It is disadvantageous that this operation must be done quickly almost at the same time as changing the speed of those crawlers, also undesirably increasing the radius of turn.
It may be possible to employ a pair of oil-hydraulic stepless speed changers to transmit power from the engine to the right and left crawlers, independently of each other. In this case, operations for speed reduction will be easier and the radius of turn will be decreased easily to a noticeable extent. However, it will become more or less difficult for the drivers to steer such a combine to run straight or along somewhat curved rows of grain stalks.
Alternatively, a single oil-hydraulic stepless speed changer may be employed in combination with an oil-hydraulic xe2x80x98steering gearxe2x80x99 or steerage. The former speed changer will transmit engine power in unison to both the crawlers, whilst the latter device increases the speed of outside crawler remote from the center of turn, reducing at the same time the speed of inside crawler facing the center of turn. Such a combine will not only be steered more easily to run straight but also will contribute to a decreased radius of turn. In this case, the combine tends to run at a constant speed whether it advances straight or turns around the center. Therefore, the driver will have to slow down the combine when it must make a xe2x80x9cspinxe2x80x9d of a very small radius of turn. Thus, the driver have to unwillingly carry out both the operations for turning the combine and for speed change thereof.
A link motion mechanism may be employed in addition to the oil-hydraulic (hereinafter referred to simply as xe2x80x98hydraulicxe2x80x99) steerage so as to automatically slow down the combine when said device is operated, and also to automatically accelerate the combine to its normal speed in harmony with a following operation for causing it to restore its straight-running mode. This way of diminishing the described problems will however give rise to another problem, and indeed, when the combine is adjusted as to its running course relative to a row of grain stalks, its running speed will increase or decrease unintentionally and at random even during normal harvesting works. In such an event, the driver will suffer from a kind of discrepancy between his feeling in driving the combine and its actual motions, disabling him to smoothly and adequately steer the combine.
In general, the driver""s manual force applied to a steering wheel or the like parts is transmitted to a xe2x80x98steering gearxe2x80x99 or steerage through a train of reduction gears. The output from the reduction gears for turning a mobile agricultural machine for example the combine is proportional to the angular displacement of the steering wheel. If in such a prior art system a particular farm on which the combine is running along a row of grain stalks to be harvested is more slippery for the crawlers than normal farms, then the combine is likely to make a smaller turning action than expected. If on the contrary the particular farm is less slippery than the normal farms, then the combine will make an overaction when turning. As a result, it is remarkably difficult for the driver to steer the combine along the row of grain stalks that have to be reaped and threshed. He will have to make his best efforts to recover a correct turning motion of the combine, relying solely on his driving sense and ability, lest the combine should turn so late or meander so seriously that it would deviate from said row of grain stalks.
The present invention provides a mobile agricultural machine that comprises a pair of right and left traction members, a transmission, a main speed change device operable to transmit at any speed ratio a driving force from an engine through the transmission to the traction members so that the traction members are driven at any traveling speeds, a steerage and a steering device operable to cause the steerage to differentiate the traveling speeds between the traction members, wherein both the transmission and the steerage of the machine have respective power-transmitting structures constructed such that a normal running load at the highest speed is substantially equal to a maximum traveling load when swiveling. Consequently, those transmission and steerage may be formed using stepless reducers almost of the same specification. Reduction ratios of the traction members to the transmission, as well as that of said members to the steerage can thus be designed readily. A sufficient traction force for swivel of a very small radius is also ensured for the traction members.
In the agricultural machine of this principle, the reduction ratio of the output from the steerage may be set greater than that of the transmission for high-speed running. In such a case, the machine can turn at lower speeds at the bare end of a farm, though it usually runs at higher speeds when driven straight for an agricultural work.
In the agricultural machine of the described principle, the reduction ratio of the output from the steerage may be set smaller than that of the transmission for low-speed running. In this alternative case, the machine can turn rapidly at the bare end of a farm, even if it is driven straight at lower speeds for doing an agricultural work.
From still another aspect of the present invention, it provides a mobile agricultural machine that comprises a pair of right and left traction members, a transmission, a main speed change device operable to transmit at any speed ratio a driving force from an engine through the transmission to the traction members so that the traction members are driven at any traveling speeds, a steerage and a steering device operable to cause the steerage to differentiate the traveling speeds between the traction members, wherein the steering device has a ridge-following position, a braked turn position and a spinning turn position, all within a range defined between a straight traveling position and a limit position for the most acute turn of the smallest radius. In this agricultural machine, the steering device can be operated not stepwise but continuously so as to select any one from three modes of following a row of grain stalks or any other plants or following a ridge in a farm, making the gentle braked turn and making the spinning turn at the bare end of said farm. Any driver can thus steer this machine with only his one hand to vary the angle of steering device. It is advantageous that simultaneously with the steering operation, the driver or worker may do with his other hand any other works such as raising or lowering any implements for performing an agricultural work.
At the ridge-following position, the machine can make slowly a very gentle turning motion of a large radius so as to advance along the row or ridge while running at a normal speed. At any spinning turn position for smaller radii, one of the traction members (viz., inside traction members) facing the center of their circular locus will be driven in a reverse direction. The position for braked turn is interposed between those two positions, so that any abrupt and sudden change in the angle of turn is prevented.
In an embodiment of the agricultural machine just summarized above, the maximum angle of steering to which the steering device can be rotated in one angular direction is set at about 135 degrees. A range from 0 degree to about 15 degrees is allotted to the straight traveling position for following the row or ridge. Therefore, the driver or worker can rotate the steering device by 135 degrees with his one hand without any difficulty, so as to cause the machine to make a spinning turn into a reversed direction relative to said rows or ridges. On the other hand, he may thereafter rotate the steering device by up to 15 degrees to gently steer the machine to follow an obtuse or gentle curvature of said row or ridge that is now to be followed.
From a further aspect of the present invention, it provides an agricultural machine comprising a pair of right and left traction members, a transmission, a main speed change device operable to transmit at any speed ratio a driving force from an engine through the transmission to the traction members so that the traction members are driven at any traveling speeds, a steerage and a steering device operable to cause the steerage to differentiate travel speeds between the traction members, wherein the steering device is operatively connected by a differentiator to the steerage in such a manner as to provide a curvilinear relationship between the angular distance or intensity of an input from the steering device to the steerage and the intensity of a resultant controlling output from said steerage. This structure is advantageous in that, even if the right and left traction members on the farm would undergo considerably different ratios of slipping along the farm""s right and left zones respectively engaging with said members, there is ensured a congruity for the worker between his feeling of steering the machine and the actual extent of the steering device""s angular displacement necessary to make the machine to follow the row or ridge. Thus, it is now possible to diminish the problems of delayed turn due to slow control or meandering run due to acute and/or excessive control. The worker can now adjust and control easily the travel course of the machine while doing an agricultural work.
Preferably, the steering device has a central position for straight run (viz., the ridge-following position in the previous embodiment ) and side regions continuing from and sandwiching said position to define a substantially constant central range of control. Such a curvilinear relationship applies only to the central range, so that this relationship then prevailing between the steering device and the steerage will automatically be switched over to a linear and proportional relationship when as said device is operated beyond and outside the central range. The machine is protected well from delay in its turning motion or from meandering when it draws curvatures of greater radii so as to adjust its course relative to the row or ridge while running at higher speeds. The worker can operate the steering device to let the machine make spinning turns of smaller radius at a bare end of the farm, with his normal feeling of driving the machine being not disturbed at all. Thus, the machine is now adapted to both the agricultural works at higher speeds and its turning at lower speeds.
In one example embodying the principle just summarized above, the ratio of a command output from the steerage per unit angular displacement of the steering device within the central range including the central position for straight run is set greater than that which is effective outside said range. In this case, the machine doing an agricultural work can be controlled adequately and quickly to adjust its course along the row or ridge, thus avoiding delay in its turning motion and affording speed-up of agricultural works.
In another example embodying the said principle, the ratio of a command output from the steerage per unit angular displacement of the steering device within the central range including the central position for straight run is set smaller than that which is effective outside said range. In this alternative case, the machine doing an agricultural work on a less slippery farm can be controlled by the worker, without disturbing his feeling of driving the machine, not only preventing it from meandering but also affording speed-up of agricultural works.
From a still further aspect of the invention, it provides a mobile agricultural machine such as a combine comprising a body, a pair of right and left traction members connected to the body, a hydraulic transmission, a differential gear apparatus, the transmission cooperating with the differential gear to transmit a driving force from an engine to the traction members to thereby drive the body at any traveling speeds, and a steering mechanism which in turn comprises a manually steering member and a hydraulic steerage operable to transmit any angular displacement of the manually steering member to the differential gear apparatus so as to differentiate travel speeds between the traction members, with the steering mechanism further comprising differentiating gears for transmitting angular displacement of the manually steering member to the hydraulic steerage. This machine is advantageous in that its body can turn either sharply or gently in response to the extent to which the manually steering member is operated.
The differentiating gears may be designed to amplify an initial output force of the manually steering member such that the machine body makes a sharper turn in response to said initial output force, as compared with the prior art usual machines. Consequently, the machine can be steered adequately and quickly free from any delay in its turning motion.
Alternatively, the differentiating gears may be designed to attenuate an initial output force of the manually steering member such that the machine body makes a gentler turn in response to said initial output force, as compared with the prior art usual machines. Due to this feature, the manually steering member is rendered more adapted for straight run of the machine, and it in turn can be steered adequately.
The manually steering member may be a steering wheel operable in a manner similar to that mounted on the prior art tractors or rice-planters. The worker will not suffer from any disturbance in his feeling of driving the machine when adjusting its travel course or making it to turn.
Alternatively, the manually steering member may be a rockable lever that is capable of rocking for instance sideways, forcing the machine to swing to the right or to the left, or causing it to make a swivel to the right or to the left turn.
A mechanical linkage may be employed to operatively connect the manually steering member to the transmission and the steerage. The linkage is free from any deterioration in its function in the course of time, thus enhancing reliability of the steering mechanism as a whole.
An electronic controller may be employed in place of the mechanical linkage also to operatively connect the manually steering member to the transmission and the steerage, thereby increasing the functional variety of the steering mechanism and also reducing manufacture cost thereof.